Track circuit



Dec. 14 ,1926. 1,610,800

w. H. B. LAVARACK TRACK CIRCUIT Filed Jan. 7, 1925 I INVENTOR BY 9 ZA'TI'ORNEY Patented Dec. 14, 1926.

WILLIAIVI H. B. LAVARACK,

TRACK Application filed Januar This invention relates to railwaysignalling, particularly track circuit signalling and more especially tothe track. circuit itself.

At the present time railway signals in approved practice are controlledby means of .what is known as a track circuit. This track circuit is aunit indefinitely repeated. The unit is a section of trackway set oilfrom the rest of the trackway by insulating joints, usually one in eachrail at each end of the section. The rails of the section at one endhave a source of electrical potential connected across them. At theother end of the section a relay is connected across the track section.Just so long as a pair of Wheels connected to a common axle is not onthe section the relay is energized by the source of potentialsutficiently to maintain its armature in an upper position, or signalcircuit closing position. If a pair of wheels connected to a common axlecomes upon the section, the relay is shunted, becomes deenergized andits armature falls or opens the signal circuit.

The whole safety of the track circuit depends upon the value in ohms ofthe shunt made by the wheels and axle. II" this resistance is very lowthe arrangement is effective, if it is very high then the possibilityexists that the relay armature will not respond and drop. Thepossibility that the relay armature will not release or drop or move toopen signal circuit position is enhanced by the fact that less currentis need ed to keep an armature in its upper position than is needed toraise it to that posi tion. In ordinary practice with direct currenttrack relays, the pickup is about seventy milliamperes whereas the dropaway is about thirty-live milliamperes. A given resistance shunt mightwell prevent an armature from being lifted but would not cause it todrop or fall.

Due to many and well known conditions i actual practice, such forinstances as, rusty wheels and rails the train shunt might rise to suchhigh value that it would not be effective to drop the relay armature butwould prevent the raising of the armature if it once dropped.

In View of the hereinbefore stated considerations applicant has for amain objectthe provision of means to most certainly insure the droppingof a track circuit relay OF NORWOOD, NEVJ JERSEY.

CIRCUIT.

y 7-, 1925. serial No. 9&8.

armature upon the entrance of a train to the section to which the relayis connected. Another object of applicants invention is to provide'ieans for actually realzing the circuit of a track circuit re ay upontire entrance of a train to the section t6 which the relay is connected.L ther object of applic s to retain every advantage i or he )resenttrack circuit arrangement in connection with his new arrangement.

(,lther objects and advantages will appear as the dos: 'iption of heparticular physical nbodiment selected to illustrate the ihvenionprogresses, and the novel feature of the invention will be particularlypointed out in the appended claims.

In describing the invention in detail, and e particular physicalembodiment selected to illustrate the invention, reference is had to theaccompanying crawing, wherein l. have illustrated a particular preferredphysical emoodiment of my invention, ahd wherein like characters ofreference desigcorresponding parts throughout the several views, and inwhich:

Figure l is a schematic representation of a well known tracl: circuitwith my invention applied thereto; Fig. 2, is a sectional VlGWillustrating a. conventional track in strument usable with my invention.

in Fig. 1, numeral 1 indicates one rail of a trackvv'ay and 2 the otherrail. The track circuit section is set oil from the TESL of the trackwayby ii'isinating joints, 3, 4-, 5 and At one end the battery 7 isconnected across the rails and at the other end the relay 8 is connectedacross the rails. The signal 9 one ized by battery 10 through a circuitpass througl'i armature 11 controls traflic over the section. All ofthis construction is old and well known and is representative ofstandard practice with end ted direct current track circuits, which hasbeen selected as most simple to illustrate the invention, althoughapplicant does not mean to exclude the use of his invention withalternating current tracl; circuits, or center or oll'set feed, as it isusable with any of the commercial standard track circuits, whether therelay derives its entire energy from the track rails or not.

In 1 it will be seen that battery 7 is connected to the rails by twoleads, 12 and 13 and that 13 goes through a diagrammatically indicateddevice 14 and emerges as 15. In the same way relay 8 is connected to therails by leads 16 and 17 and that 1'? passes through a similar device 1%and emerges as 18. The insertion of these devices ll in the leads 13 and17 is the way in which applicant expresses the idea of his invention.

The device designated as a whole by 1e conventionally illustrated byFig. 2. The device 14: is old and well known and exists in many forms,but as no particular form is essential to the expression of applicant sinvention, a conventional form merely has been illustrated. This device1st is known as a track instrument and is merely a means whereby apassing train may by mechanical action cause a change in a circuit. inthe form shown the device consists of lever 19 suitably pivoted, as toatie 20, by pin 21 and the lever by end 22 bears against rail 1. As iswell understood by those skilled in railway track work, when a trainpasses over the rail 1 there is relative move ment between the tie 20and the rail 1. T his movement results in depressing end 22 an raisingend 23. End 23 is connected, as by link 24 to a conducting member 25which bridges terminals 26 and 27. When end 23 rises, bridge 25 risesand disconnects 2S and 27 and so lead 1-5 and lead 13, insulation beingplaced at proper points as 28, 29, 30, 31 and 3-1 to prevent undesiredelectrical paths.

The operation of the device is quite obvious. A train entering thesection in, the direction of trailic, as shown by the arrow A, wouldoperate track instrument ll at the signal 9 and break the circuitthrough 1'? and 18 and so the source of potential would be entirely cutoil from the relay 3, so that the armature would have to drop regardlessof the value in ohms or" the shunt formed by the wheels and axles. inshort there is an absolute break in the circuit, so that the means usedto drop the relay armature is absolute and positive and not marginal.

' Applicant has also shown a track instrument 14: inserted in one of theleads oi battery 7. This may or may not be done. If there is nonecessity for movement against the normal direction of traffic this maybe dispensed with but for complete protection it should be used becauseat times trains may enter the section from the end which the source ofpotential is positioned.

It is to be observed that although applicant has introduced into theordinary and well known track circuit, another element, nevertheless,the track circuit may function just as it now does it the added elementfails to operate. The shunt now depended upon to deenergize a trackrelay is just as eilective in applicants arrangement as in any trackcircuit. It applicants added element becomes deranged so that thecircuit is broken. therethrough improperly then the failure is on theside of safety as the signal would be plz (i at danger position thereby.

Although particu 4 l nave described the construction of one physicalembodiment oi my invention, and explained the operation and principlethereof, nevertheless, I desire to have it understood that the formselected is merely illustrative, but does not :haust the possiblephysical embodiments f the idea oi? means underlying my invention. 1What T claim as new and desire to secure ov d Matters Patent of theUnited States, is:

1. In a tract circuit, in combination: rails; a source of potentialconnected across the i .ils at one point, a relay connected across therails at another point and means operable mechanically by a passingtrain inserted in a connection of the relay for breaking the rircuitthereof.

2. In track circuit, in combination: rails; a source oi potentialconnected across the rails at one point; a relay connected across therails at another point and means including a circuit controller operablemechanically by a passing train inserted in connection of the relay.

.ln a track circuit, in combination: rails; source oi potentialconnected across he rails at one point; a relay connected ross the railsat another point and means associated with the rail adjacent the relayJassing train for breaking the rac circuit, in combination: urce orpotential connected across one point; a relay connected across the railsat another point and means operable mechanically by a passing train forbreaking the source oi potential circuit. o. in a track circuit, incombination: rails; a source of potential connected across the rails onepoint; a relay connected the rails at another point and means operableby a passing train tor breaking the relay circuit and means operable bya passing train for breaking the source of potential circuit.

6. in a circuit in combination: rails; a source of potential connectedacross the rails one point; a relay connected across the rails atanother oint wh reby a pass ing train will shunt the relay and meanswhereby the relay circuit will be broken even if it is is not properlyshunted by a train spanning the ails at its point of connection.

WllLLlAll /l H, B. LAVARACK.

